Liverpool - Gerry McIlroy was £100 000 richer on Sunday following his son Rory's two-stroke victory in the 143rd Open Championship at Royal Liverpool.
Ladbrokes said in a news release that Gerry had placed a 500/1 bet on his son a decade ago to land the coveted Claret Jug within 10 years.
"Although we're facing heavy losses we can't help but admire the foresight of Rory's dad and his pals a decade ago," added a spokesperson for the British bookmakers.
Two friends of Rory's father also collected nearly £80 000 from a similar wager.
"They are all going to be very happy," said McIlroy junior. "My dad has never reminded me but I knew he'd done it. It's a nice little bonus."
McIlroy's victory, his third in a major after the 2011 US Open and 2012 US PGA Championship triumphs, means he only needs the Masters to complete a grand slam of golf's 'Big Four' prizes.
"It's an 8/1 shot McIlroy wears the Green Jacket at Augusta in 2015 and just 1/2 at any time in his career," said Ladbrokes.